RU135545U1 - DEVICE FOR CLEANING METAL SURFACES FROM PAINT AND OXY CONTAMINATION - Google Patents

Abstract

1. A device for cleaning metal surfaces from paint and oxide contamination, consisting of a high-frequency generator, a switching element, a coaxial waveguide cable, characterized in that it consists of a high-potential electrode and a low-potential electrode, between which there is a contaminated metal surface and an insulating insert on the high-potential side an electrode that is connected in series with a high-frequency generator, a power regulator of a high-frequency generator, commutator iring element and power connection circuit, respectively. 2. A device for cleaning metal surfaces from paint and oxide contaminants according to claim 1, characterized in that the function of a low-potential electrode is performed by a grounded metal surface on which there is paint and oxide pollution.

Description

The device relates to the technology of repair production and is intended to clean the surface of metal products from paint and formed oxide contaminants.

One of the technological operations during the repair of a product is its cleaning. Product cleaning is usually carried out using mechanical devices and devices (brushes, cleaning devices, abrasives). After several cleaning cycles, the metal surface becomes rough, and in some cases, its geometric dimensions change and it becomes unsuitable for further use.

A known method of cleaning the surface of metal products, such as pipes, from paint and other coatings, implemented in a device for cleaning pipe surfaces [1]. This device is equipped with a heating element in the form of a piece of pipe placed coaxially on the pipe being cleaned and connected via an electrical contact at one end to the pipe. The other end of the heating element and the pipe are connected to an AC source. The cleaning of the pipe surface in this device is achieved due to the fact that the electric current flowing along the inner surface of the pipe of the heating element and the outer surface of the pipe being cleaned heats the pipe surface to a high temperature, causing cracking and delamination due to differences in the linear expansion coefficients of the metal and coating coatings from the surface being cleaned.

This method is implemented using a device in which two electrodes are placed on the surface to be cleaned from the side of the paint layer and high voltage pulses are applied to them, while the distance between the electrodes is set to be greater than the sum of the thicknesses of the paint layer at the places of installation of the electrodes. When high voltage pulses are applied to the electrodes, an electrical breakdown of the paint layer occurs between the electrodes and the product. Further discharge passes along the interface between the product and the paint, while the expanding discharge plasma detaches the paint from the surface being cleaned. The disadvantage of this cleaning device is the low cleaning performance, due to the long heating, moving and installing electrodes on the surface being cleaned. Another disadvantage is the insufficient quality of processing of the surface being cleaned due to the appearance of fusion areas on it (or burning on a thin-walled product) in places of electrical breakdown of the paint layer.

Known methods for treating the surface of products by an arc discharge in vacuum and devices for their implementation, based on the impact on the treated surface of rapidly moving cathode spots of a vacuum-arc discharge. So, for example, [2] “A method for surface treatment of products by an arc discharge in vacuum and a device for its implementation” includes the claimed method and device for its implementation. It contains an arc power source, a positive electrode and, as a cathode, a workpiece placed in a vacuum. In this case, the negative potential current leads are connected to the surface to be treated at two or more points through current regulators.

The main disadvantage of this device is that the result is achieved under conditions of creating a vacuum in it, which is difficult to achieve under industrial conditions. Numerous connection points and the presence of a current regulator greatly complicate the device. All this complicates the use of this device in industry. In addition, the disadvantage of the cleaning device according to [2] is the low quality of cleaning.

The closest analogue is a device for cleaning the surface of a metal product from paint [3]. The device consists in the fact that the surface of the metal product under the paint is heated by electric currents, and the device contains an alternating current generator connected in series, a switching device, a load balancing device and an inductor. The device is placed near the cleaned surface of the metal product from the side of the paint layer and by short-term induction heating the temperature of the cleaned surface of the metal product is adjusted to the temperature of gas emission from the paint at the metal-paint interface, followed by a sharp removal of the paint layer formed by the gases from the cleaned surface of the metal product. The disadvantage of this device is that when induction heating occurs, the metal is heated, similar to the process of quenching by high-frequency currents with a change in its mechano-physico-chemical composition, moreover, when this device is used, thermal expansion of the material occurs, its cracking, warping, which limits the scope of use this device. The heating of massive parts of the metal surface being cleaned leads to high energy consumption. The disadvantage is the need to perform special safety measures to protect service personnel from thermal burns.

The technical task of the proposed device is the cleaning of metal surfaces from paint and oxide contaminants without mechanical and high-temperature effects on the cleaning object.

The problem is solved by the proposed device for cleaning metal surfaces from paint and oxide contamination, consisting of a high-frequency generator, a switching element, a coaxial waveguide cable, characterized in that it consists of a high-potential electrode and a low-potential electrode between which there is a contaminated metal surface, and an insulating insert on the side high-potential electrode, which is connected in series with a high-frequency generator, regulator power of a high-frequency generator, a switching element and a power connection circuit, respectively. In this case, the function of a low-potential electrode is performed by a grounded metal surface on which there is paint and oxide pollution.

The essence of the device is illustrated by drawings.

Figure 1 is a General diagram of a device for cleaning metal surfaces from paint and oxide contaminants.

Figure 2 presents a schematic diagram of a composite working capacitor.

Figure 3 shows the dependence of the specific power of dielectric heating on the capacitance of the working capacitors formed by the air gap, paint and oxide materials.

Figure 1 shows the general diagram of a device for cleaning metal surfaces from paint and oxide contamination, the numbers indicate: power circuit for connecting a high-frequency generator 1, switching element 2, power control device for a high-frequency generator 3, high-frequency generator 4, grounding (low-potential circuit) 5, coaxial waveguide cable 6, paint and oxide pollution 7, high-potential electrode 8, low-potential electrode (with a metal surface to be cleaned) 9, insulating insert 1 0.

Figure 2 presents a schematic diagram of a composite working capacitor, which consists of a power connection circuit of the device 1, a switching element 2, a power regulator of a high-frequency generator 3, a high-frequency generator 4, grounding (low-potential circuit) 5, a coaxial cable waveguide 6 of paint and oxide pollution 7, a high potential electrode 8, a low potential electrode (with a metal surface to be cleaned) 9, an insulating insert 10, composite capacitors of the working capacitor, and , B, C - sectional planes, C _{a, C,} C _c1, C _c2 - paint and capacitors formed by oxide contaminants, air gap, paint and oxide contaminants and air layer, respectively, in the corresponding sectional plane, L is the length of the metal product.

Figure 3 presents the obtained experimental curve of the specific power of dielectric heating spent on heating paint and oxide contaminants depending on the capacity of the working capacitors formed by the air gap, paint and oxide materials (in the shown dependence - paint and oxides of oils and oil products) ε _die and mixed air-paint-and-oxide polluting materials ε _air - ε _diel between capacitor plates.

The operation of the device shown in figure 1, figure 2 is as follows. The device is connected from the power voltage supplied to the contacts 1. Switching on and off, including the protective one, is carried out by the switching element 2, and the power of the high-frequency generator is set by the regulator 3. The high-potential output of the high-frequency generator 4 is connected to the high-potential electrode using a coaxial waveguide cable 6 device 8, placed on the side of the polluting layer of paint and oxide pollution 7, near the cleaned metal surface of the product 9. Low-pot The special electrode of the high-frequency generator is connected to the ground 5 by the live parts of the metal surface 9 being cleaned. Between the high-potential electrode 8 and the low-potential electrode 9, an insulating insert 10 is located that prevents direct contact of the electrodes and compensates for irregularities and manufacturing errors of the metal surface to be cleaned. Thus, the presented design of the device forms a working capacitor. After turning on the high-frequency generator, the RF energy flowing through the coaxial waveguide cable 6 and arriving at the high-potential electrode 8 on the one hand and through the grounded low-potential electrode on the other hand forms a high-frequency field that implements dielectric heating in the working capacitor, which affects the paint and oxide materials 7 polluting the metal surface 9. Due to dielectric heating, the paint and oxide materials 7 heat up and begin to degrade, turning into opodobnuyu mass, which is accompanied by peeling and removing a cleaned metal surface 9. The efficacy and quality of cleaning metal surfaces of paint and oxide impurities are increased when using powerful RF fields excited using powerful generators in a relatively short time interval. In this case, the field power (power of the used generator) and the exposure duration are in a predetermined ratio: the higher the power, the shorter the heating of paint and oxide materials. Moreover, the power of the generator and the duration of the heating are selected based on compliance with the requirements of the duration of the heating of the entire paint layer and oxide contaminants to the temperature of their destructive transformation.

The principle of regulating the process of high-frequency exposure to dielectric materials is shown in [4], where the dynamics of the phase state (the beginning of destructive changes) of the processed material is determined depending on the anode current of the high-frequency generator. Thus, according to the readings of the anode current ammeter, standardly installed on most industrial high-frequency installations, the value of the anode current is determined, which corresponds to the phase transformation (destruction) of paints and oxide contaminants on metal surfaces.

The working capacitor and the position of the polluting material on the metal surface to be cleaned can be represented as a series of unlike capacitors (Fig. 2) with proportional charges depending on the thickness and composition of the paint and the polluting oxide between the plates of these capacitors. These capacitors are part of the working capacitor of a high-frequency electrothermal installation. The main calculations of the theory of dielectric heating, which determine the operating procedure of the proposed device are presented in the appendix.

Figure 2 presents a schematic diagram of a composite working capacitor, which consists of a power connection circuit of the device 1, a switching element 2, a power regulator of a high-frequency generator 3, a high-frequency generator 4, grounding (low-potential circuit) 5, a coaxial cable waveguide 6 of paint and oxide pollution 7, high potential electrode 8, low potential electrode (with a metal surface to be cleaned) 9, insulating inserts 10, composite capacitors of the working capacitor, and , B, C - sectional planes, C _a, C _a, C _c1, C _c2 - capacitors formed paint and oxide contamination, an air gap, paint and oxide contaminants and air layer, respectively, in the respective section planes, L - the length of the metal product. From the presented figure (figure 2), you can determine the capacitance of a composite working capacitor:

Or in the general case, the calculation of the capacitance of a composite working capacitor along the entire length L of the surface to be cleaned can be done by the formula:

The air gap located between the plates of the capacitors C _a , C _c2 (Fig. 2) significantly reduces the capacitance of the composite capacitor, therefore, the areas that are directly in contact with paint and oxide contaminants are primarily affected (C _in is a composite capacitor without an air gap). Thus, the effect of selectivity of high-frequency exposure is realized. A decrease in the intensity of processing in this place occurs after the destruction of paint and oxide pollution, the formation of an ash-like mass. The next place of intense exposure is the zone of capacitors (C _c1 -C _c2 ) with the closest location of the polluting elements (paint and oxide pollution) with the surface of the plates of the capacitors, etc.

The process will automatically end after a high-frequency exposure to all available paint elements and oxide contaminants located between the capacitor plates (self-regulation effect).

These features of the device increase the energy efficiency of the cleaning process, because only the surface contaminating paint and oxide contaminants are heated, and does not have a temperature, and hence mechanical, physico-chemical effect on the metal surface being cleaned. The absence of heating of the metal being cleaned (it is a low-potential-grounded electrode) creates safe working conditions.

Figure 3 presents the obtained experimental curve of the specific power of dielectric heating spent on heating paint and oxide contaminants depending on the capacity of the working capacitors formed by the air gap, paint and oxide materials (in the shown dependence - paint and oxides of oils and oil products) ε _die and mixed air-paint-and-oxide polluting materials ε _air - ε _diel between capacitor plates.

The power curve spent on dielectric heating shows a significant increase in power (and therefore the impact efficiency) with an increase in the capacitance of the working capacitor (in our device, one of the plates of which is a cleaned metal surface). In the presence of a large amount of air gap (places where there is no paint and oxide contamination on the metal surface being cleaned) they have a small capacitor capacitance and are not exposed to high-frequency effects.

In places with a large number of elements polluting the metal surface, the capacitor power is high and, accordingly, the RF effect is large, aimed at dielectric heating of these contaminants, which leads to their destructuring and the formation of an ash-like mass.

Example. When the space between the plates of the working capacitor with an area of 100 cm ^{2 is} completely filled with Buxol lubricant oxides and oil-based paint when using high-frequency heating equipment, model УЗП 2500, with an operating frequency of 27.12 MHz, and a total power of 2.5 kW, in a steady state the operating mode of the equipment, the dielectric heating power was 200 watts. When filling with lubricant oxides and paint based on oil components less than 10% of the volume (the rest is the air gap) of the space between the plates of the working capacitor, the power was about 10 watts. From the presented it can be seen that the power curve of dielectric heating depends on the capacitance of the working capacitor, which directly depends on the filling of the interelectrode space with paint and polluting oxides.

Practical testing of the device was realized when processing the inner surface of the pipe using high-frequency equipment of the UZP-2500 model with an operating frequency of 27.12 MHz. In this case, a high-potential electrode with a diameter of 50.5 mm was placed in a pipe with a diameter of 57 mm, acting as a low-potential electrode, with paint elements and polluting oxide materials on its inner surface. An insulating insert 0.3 mm thick was placed between the high-potential electrode and the inner surface of the pipe . As an insulating material, we took cardboard insulating grade PTK BiK, GOST 2824-86, 0.3 mm thick. The electrophysical properties of this cardboard correspond to all the parameters of the insulating material, and the low cost and availability allows it to be used as a disposable consumable. The exposure time ranged from 21 to 36 seconds, depending on the degree of contamination. The ammeter readings corresponding to the anode current of the RF exposure were 0.6 A. The destruction of the degraded paint and the polluting oxide was carried out manually, together with a disposable insulating material, which also facilitated, by absorbing, the removal of liquid fractions of the polluting material. During the cleaning process, the layer of paint and polluting oxide was degraded and partially crumbled from the surface. Turning it into easily removable ash-like substances allowed us to organize the process of final removal of cleaning products. The use of the proposed device for cleaning a metal surface from paint and oxide pollution showed a satisfactory quality of cleaning.

Information sources

1. The author's certificate of the USSR No. 1313537, MKI V08V 7/04, 1987

2. Patent RU No. 2457282, IPC C23F 4/00, 18/02 2011

3. Patent RU No. 2365435, IPC V08V, 27/08 2009, (prototype).

4.Filippenko N.G., Livshits A.V., Mashovich A.Ya. Automation of the process of high-frequency heating of materials at an industrial plant UZP 2500 // Modern technologies. System analysis. Modeling. - Irkutsk, 2011. Issue 2 (30). S.193-198.

Appendix to the description of the device for cleaning metal surfaces from paint and oxide pollution

The proposed device is used in industrial equipment of high-frequency dielectric heating. When determining the operating mode of the device, the principle of dielectric heating operation was presented in the source [1], according to which the power of high-frequency (HF) exposure released in a unit volume of the dielectric (which is paint and oxide pollution) is determined by the dielectric heating formula:

where: R _beats. - specific power of dielectric loss, W / cm ³ ; E is the electric field strength; V / m; f is the field frequency, Hz; ε is the relative dielectric constant; tanδ is the dielectric loss tangent.

An explanation of the physical processes that occur in polymeric materials when their dielectric parameters change is found in [2], where the dielectric loss tangent tanδ of the polymeric material is found through the electrical parameters of the high-frequency generator operating mode — current I _ao and voltage U _p on the working capacitor and defined as follows:

where: _P - the working capacitor of the RF installation; x _St = ωL _{communication} - reactance element coupling between circuits, ω - angular frequency, C _e - equivalent capacitance generating lamp comprising mounting capacity, L _binding - inductance coupling element, U _p - rms voltage at the working capacitor, γ - factor the first harmonic of the anode current pulse, r ₁ is the resistance of active losses in the primary (anode) circuit.

In industrial-type installations operating in the under-stressed mode of operation of a high-frequency generator (U _p = const, ω = const), taking

into account the ability to control the electrophysical parameters of the RF installation, the formula (2) will have the form:

Substituting the obtained value in (1), we have:

Taking into account the established process of RF exposure (regulation is complete), we can take E = const, and, according to the design conditions of industrial electrothermal installations, also f = const.

Therefore (4) will have the following form:

Formula (5) can be taken as evidence of the intensity of the influence of RF energy on dielectric materials, depending on the capacitance of the working capacitors and the relative dielectric constant of the paint and oxide contaminants located between the capacitor plates, one of which is the metal surface being cleaned.

Information sources

1. Netushil A.V., Zhukhovitsky B., I., Kudin V.N. High-frequency heating of dielectrics and semiconductors. // M .: Gosenergoizdat, 1959. - 480 s

2. Yulenets Yu.P., Markov A.V. Determination of the dielectric loss tangent and moisture content by the parameters of the electric mode of the high-frequency heating installation // News of Universities. Instrument Engineering, 1997. - T. 40. - No. 5. - S.60-65.

Note:

An example of a selectivity effect is a locally water-soaked paper towel. In our case, paint and polluting oxides. When certain electrical potentials are applied to the surfaces of the wipe, partial through conductivity will begin only in wetted areas.

An example of a self-regulating effect is a water-soaked paper towel. When certain electrical potentials are brought to the surfaces of the wipe, through conductivity will begin, which will lead to its heating, evaporation of moisture and a change in its (wet wipe) electrophysical parameters. The process will end automatically after complete removal of moisture (drying).

Claims (2)

1. A device for cleaning metal surfaces from paint and oxide contamination, consisting of a high-frequency generator, a switching element, a coaxial waveguide cable, characterized in that it consists of a high-potential electrode and a low-potential electrode, between which there is a contaminated metal surface and an insulating insert on the high-potential side an electrode that is connected in series with a high-frequency generator, a power regulator of a high-frequency generator, commutator iring element and power connection circuit, respectively. 2. A device for cleaning metal surfaces from paint and oxide contaminants according to claim 1, characterized in that the function of a low-potential electrode is performed by a grounded metal surface on which there is paint and oxide pollution.

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